Biomechanical and histomorphometric esophageal remodeling in type 2 diabetic GK rats

Mechanical experimentation of the gastrointestinal tract: a systematic review

The gastrointestinal (GI) organs of the human body are responsible for transporting and extracting nutrients from food and drink, as well as excreting solid waste. Biomechanical experimentation of the GI organs provides insight into the mechanisms involved in their normal physiological functions, as well as understanding of how diseases can cause disruption to these. Additionally, experimental findings form the basis of all finite element (FE) modelling of these organs, which have a wide array of applications within medicine and engineering. This systematic review summarises the experimental studies that are currently in the literature (n = 247) and outlines the areas in which experimentation is lacking, highlighting what is still required in order to more fully understand the mechanical behaviour of the GI organs. These include (i) more human data, allowing for more accurate modelling for applications within medicine, (ii) an increase in time-dependent studies, and (iii) more sophisticated in vivo testing methods which allow for both the layer- and direction-dependent characterisation of the GI organs. The findings of this review can also be used to identify experimental data for the readers' own constitutive or FE modelling as the experimental studies have been grouped in terms of organ (oesophagus, stomach, small intestine, large intestine or rectum), test condition (ex vivo or in vivo), number of directions studied (isotropic or anisotropic), species family (human, porcine, feline etc.), tissue condition (intact wall or layer-dependent) and the type of test performed (biaxial tension, inflation-extension, distension (pressure-diameter), etc.). Furthermore, the studies that investigated the time-dependent (viscoelastic) behaviour of the tissues have been presented.

Experimental investigations of the human oesophagus: anisotropic properties of the embalmed mucosa-submucosa layer under large deformation

Mechanical characterisation of the layer-specific, viscoelastic properties of the human oesophagus is crucial in furthering the development of devices emerging in the field, such as robotic endoscopic biopsy devices, as well as in enhancing the realism, and therefore effectiveness, of surgical simulations. In this study, the viscoelastic and stress-softening behaviour of the passive human oesophagus was investigated through ex vivo cyclic mechanical tests. Due to restrictions placed on the laboratory as a result of COVID-19, only oesophagi from cadavers fixed in formalin were allowed for testing. Three oesophagi in total were separated into their two main layers and the mucosa-submucosa layer was investigated. A series of uniaxial tensile tests were conducted in the form of increasing stretch level cyclic tests at two different strain rates: 1% s[Formula: see text] and 10% s[Formula: see text]. Rectangular samples in both the longitudinal and circumferential directions were tested to observe any anisotropy. Histological analysis was also performed through a variety of staining methods. Overall, the longitudinal direction was found to be much stiffer than the circumferential direction. Stress-softening was observed in both directions, as well as permanent set and hysteresis. Strain rate-dependent behaviour was also apparent in the two directions, with an increase in strain rate resulting in an increase in stiffness. This strain rate dependency was more pronounced in the longitudinal direction than the circumferential direction. Finally, the results were discussed in regard to the histological content of the layer, and the behaviour was modelled and validated using a visco-hyperelastic matrix-fibre model.

Experimental investigations of the human oesophagus: anisotropic properties of the embalmed muscular layer under large deformation

The oesophagus is a primarily mechanical organ whose material characterisation would aid in the investigation of its pathophysiology, help in the field of tissue engineering, and improve surgical simulations and the design of medical devices. However, the layer-dependent, anisotropic properties of the organ have not been investigated using human tissue, particularly in regard to its viscoelastic and stress-softening behaviour. Restrictions caused by the COVID-19 pandemic meant that fresh human tissue was not available for dissection. Therefore, in this study, the layer-specific material properties of the human oesophagus were investigated through ex vivo experimentation of the embalmed muscularis propria layer. For this, a series of uniaxial tension cyclic tests with increasing stretch levels were conducted at two different strain rates. The muscular layers from three different cadaveric specimens were tested in both the longitudinal and circumferential directions. The results displayed highly nonlinear and anisotropic behaviour, with both time- and history-dependent stress-softening. The longitudinal direction was found to be stiffer than the circumferential direction at both strain rates. Strain rate-dependent behaviour was apparent, with an increase in strain rate resulting in an increase in stiffness in both directions. Histological analysis was carried out via various staining methods; the results of which were discussed with regard to the experimentally observed stress-stretch response. Finally, the behaviour of the muscularis propria was simulated using a matrix-fibre model able to capture the various mechanical phenomena exhibited, the fibre orientation of which was driven by the histological findings of the study.

The Esophagiome: concept, status, and future perspectives

The term "Esophagiome" is meant to imply a holistic, multiscale treatment of esophageal function from cellular and muscle physiology to the mechanical responses that transport and mix fluid contents. The development and application of multiscale mathematical models of esophageal function are central to the Esophagiome concept. These model elements underlie the development of a "virtual esophagus" modeling framework to characterize and analyze function and disease by quantitatively contrasting normal and pathophysiological function. Functional models incorporate anatomical details with sensory-motor properties and functional responses, especially related to biomechanical functions, such as bolus transport and gastrointestinal fluid mixing. This brief review provides insight into Esophagiome research. Future advanced models can provide predictive evaluations of the therapeutic consequences of surgical and endoscopic treatments and will aim to facilitate clinical diagnostics and treatment.

Ravages of Diabetes on Gastrointestinal Sensory-Motor Function: Implications for Pathophysiology and Treatment

Symptoms related to functional and sensory abnormalities are frequently encountered in patients with diabetes mellitus. Most symptoms are associated with impaired gastric and intestinal function. In this review, we discuss basic concepts of sensory-motor dysfunction and how they relate to clinical findings and gastrointestinal abnormalities that are commonly seen in diabetes. In addition, we review techniques that are available for investigating the autonomic nervous system, neuroimaging and neurophysiology of sensory-motor function. Such technological advances, while not readily available in the clinical setting, may facilitate stratification and individualization of therapy in diabetic patients in the future. Unraveling the structural, mechanical, and sensory remodeling in diabetes disease is based on a multidisciplinary approach that can bridge the knowledge from a variety of scientific disciplines. The final goal is to increase the understanding of the damage to GI structures and to sensory processing of symptoms, in order to assist clinicians with developing an optimal mechanics based treatment.

Diabetes-induced mechanophysiological changes in the esophagus

Esophageal disorders are common in diabetes mellitus (DM) patients. DM induces mechanostructural remodeling in the esophagus of humans and animal models. The remodeling is related to esophageal sensorimotor abnormalities and to symptoms frequently encountered by DM patients. For example, gastroesophageal reflux disease (GERD) is a common disorder associated with DM. This review addresses diabetic remodeling of esophageal properties and function in light of the Esophagiome, a scientifically based modeling effort to describe the physiological dynamics of the normal, intact esophagus built upon interdisciplinary approaches with applications for esophageal disease. Unraveling the structural, biomechanical, and sensory remodeling of the esophagus in DM must be based on a multidisciplinary approach that can bridge the knowledge from a variety of scientific disciplines. The first focus of this review is DM-induced morphodynamic and biomechanical remodeling in the esophagus. Second, we review the sensorimotor dysfunction in DM and how it relates to esophageal remodeling. Finally, we discuss the clinical consequences of DM-induced esophageal remodeling, especially in relation to GERD. The ultimate aim is to increase the understanding of DM-induced remodeling of esophageal structure and sensorimotor function in order to assist clinicians to better understand the esophageal disorders induced by DM and to develop better treatments for those patients.

Esophageal morphometric and biomechanical changes during aging in rats

BACKGROUND

Human studies have demonstrated aging-related changes in esophagus which may contribute to the increased rate of gastro-esophageal reflux in elderly. The aim of this study was to investigate esophageal morphometric and biomechanical remodeling in aging rats to obtain detailed information about aging-related changes.

METHODS

Twenty-four male Wistar rats, aged from 6 to 22 months, were studied. Morphometric data were obtained by measuring the wall thickness and cross-sectional area. The esophageal diameter and length were obtained from digitized images of the segments at preselected luminal pressure levels and at no-load and zero-stress states. Circumferential and longitudinal stresses (force per area) and strains (deformation) were computed from the length, diameter and pressure data, and from the zero-stress state geometry.

KEY RESULTS

The esophageal parameters such as the weight per unit length, the wall thickness and the wall cross-sectional area increased slightly from 6 to 22 months (p < 0.05 to p < 0.001). The opening angle gradually decreased during aging (p < 0.05). The interface between the mucosa-submucosa and muscle layers slightly moved outwards and the neutral axis moved inwards during aging. The stress-strain data showed that the esophageal wall became stiffer circumferentially and longitudinally during aging (p < 0.05, p < 0.01). However, the circumferential wall stiffness showed no further change after 12 months.

CONCLUSIONS & INFERENCES

A pronounced morphometric and biomechanical remodeling occurred in the rat esophagus during aging.

Advanced glycation end-product expression is upregulated in the gastrointestinal tract of type 2 diabetic rats

AIM: To investigate changes in advanced glycation end products (AGEs) and their receptor (RAGE) expression in the gastrointestinal (GI) tract in type 2 diabetic rats.

METHODS: Eight inherited type 2 diabetic rats Goto-Kakizak (GK) and ten age-matched normal rats were used in the study. From 18 wk of age, the body weight and blood glucose were measured every week and 2 wk respectively. When the rats reached 32 wk, two-centimeter segments of esophagus, duodenum, jejunum, ileum, and colon were excised and the wet weight was measured. The segments were fixed in 10% formalin, embedded in paraffin and five micron sections were cut. The layer thickness was measured in Hematoxylin and Eosin-stained slides. AGE [N epsilon-(carboxymethyl) lysine and N epsilon-(carboxyethyl)lysine] and RAGE were detected by immunohistochemistry staining and image analysis was done using Sigmascan Pro 4.0 image analysis software.

RESULTS: The blood glucose concentration (mmol/L) at 18 wk age was highest in the GK group (8.88 ± 1.87 vs 6.90 ± 0.43, P < 0.001), a difference that continued to exist until the end of the experiment. The wet weight per unit length (mg/cm) increased in esophagus, jejunum and colon from the normal to the GK group (60.64 ± 9.96 vs 68.56 ± 11.69, P < 0.05 for esophagus; 87.01 ± 9.35 vs 105.29 ± 15.45, P < 0.01 for jejunum; 91.37 ± 7.25 vs 97.28 ± 10.90, P < 0.05 for colon). Histologically, the layer thickness of the GI tract was higher for esophagus, jejunum and colon in the GK group [full thickness (μm): 575.37 ± 69.22 vs 753.20 ± 150.41, P < 0.01 for esophagus; 813.51 ± 44.44 vs 884.81 ± 45.31, P < 0.05 for jejunum; 467.12 ± 65.92 vs 572.26 ± 93.60, P < 0.05 for colon]. In esophagus, the AGE and RAGE mainly distributed in striated muscle cells and squamous epithelial cells. The AGE distribution was much stronger in the GK group compared to the normal group both in the striated muscle layer and mucosa layer (immuno-positive area/ total measuring area %: 4.52 ± 0.89 vs 10.96 ± 1.34, P < 0.01 for muscle; 8.90 ± 2.62 vs 22.45 ± 1.26, P < 0.01 for mucosa). No visible difference was found for RAGE distribution between the two groups. In the intestine AGE and RAGE distributed in epithelial cells of villi and crypt. RAGE was also found in neurons in the myenteric and submucosal plexus. The intensity of AGE staining in mucosa of all segments and RAGE staining in neurons in all segments were strongest in the diabetes group. Significant difference for AGE was found in the epithelial cells of villi and crypt in duodenum (immuno-positive area/total measuring area %: 13.37 ± 3.51 vs 37.48 ± 8.43, P < 0.05 for villi; 0.38 ± 0.12 vs 1.87 ± 0.53, P < 0.05 for crypt) and for RAGE in neurons of all segments (e.g., for jejunum: no staining neurons% 0 vs 0, mild 36.0 ± 5.2 vs 28.7 ± 3.5, moderate 53.2 ± 4.8 vs 55.8 ± 5.4, strong 10.7 ± 1.1 vs 15.4 ± 2.0, P < 0.05). In the colon, RAGE was primarily found in neurons in the myenteric and submucosal plexus. It was stronger in the diabetes group than in the normal group (no staining neurons% 6.2 ± 0.2 vs 0.3 ± 0.04, mild 14.9 ± 2.1 vs 17.6 ± 1.5, moderate 53.1 ± 4.6 vs 44.7 ± 4.4, strong 25.6 ± 18 vs 43.6 ± 4.0, P < 0.05). In the rectum, RAGE was primarily found in the mucosa epithelial cells.

CONCLUSION: The AGE and RAGE expression was up-regulated in the GI tract of GK diabetic rats and may contribute to GI dysfunction in type 2 diabetic patients.

Stress-strain analysis of contractility in the ileum in response to flow and ramp distension in streptozotocin-induced diabetic rats--association with advanced glycation end product formation

This study compared the ileal contractility and analyzed the association between contractility with advanced glycation end product (AGE) formation in normal and streptozotocin (STZ)-induced diabetic rats. Nine STZ-induced diabetic rats (Diabetes group) and 9 normal rats (Normal group) were used. The motility experiments were carried out on ileums in organ baths containing physiological Krebs solution. Ileal pressure and diameter changes were obtained from basic, flow-induced and ramp distension-induced contractions. The frequency and amplitude of contractions were analyzed from pressure-diameter curves. Distension-induced contraction thresholds and maximum contraction amplitude of basic and flow-induced contractions were calculated in terms of stress and strain. AGE and its receptor (RAGE) in the layers were detected by immunohistochemistry staining. The maximum stress of flow-induced contractions was lowest in the Diabetes Group (P<0.05). During ramp distension, the pressure and stress thresholds and Young's modulus to induce phasic contraction were lowest in the Diabetes Group (P<0.05 and P<0.01). AGE and RAGE expressions in the different ileum layers were highest in the Diabetes group. The contraction pressure and stress thresholds were significantly associated with AGE expression in the muscle layer and RAGE expression in mucosa epithelium and neurons. The diabetic intestine was hypersensitive to distension for contraction induction. However, the contraction force produced by smooth muscle was lowest in diabetic rats. Increased AGE/RAGE expression was associated with the contractility changes in diabetic rats.

Stress-strain analysis of jejunal contractility in response to flow and ramp distension in type 2 diabetic GK rats: effect of carbachol stimulation

Investigation of intestinal motility in a genetic model of GK rats abandons the possible neurotoxic effect of streptozotocin in streptozotocin-induced diabetic model. Seven GK male rats (GK group) and nine normal Wistar rats (Normal group) were used in the study. The motility experiments were carried out in an organ bath containing physiological Krebs solution. Before and after 10(-5)M carbachol application, the pressure and diameter changes of jejunum were obtained in relation to (1) basic contraction, (2) flow-induced contraction with different outlet resistance pressures and (3) contractions induced by ramp distension. The frequency and amplitude of contractions were analyzed from pressure-diameter curves. Distension-induced contraction thresholds and maximum contraction amplitude of basic and flow-induced contractions were calculated in terms of stress and strain. (1) The contraction amplitude increased to the peak value in less than 10s after adding carbachol. More than two peaks were observed in the GK group. (2) Carbachol decreased the pressure and stress threshold and Young's modulus in the GK group (P<0.01). (3) Carbachol increased the maximum pressure and stress of flow-induced contractions at most outlet pressure levels in both two groups (P<0.001). Furthermore, the flow-induced contractions were significantly bigger at low outlet pressure levels in GK group (P<0.05 and P<0.01). (4) The contraction frequency, the strain threshold and the maximum contraction strain did not differ between the two groups (P>0.05) and between before and after carbachol application (P>0.05). In GK diabetic rats, the jejunal contractility was hypersensitive to flow and distension stimulation after carbachol application.

Morpho-mechanical intestinal remodeling in type 2 diabetic GK rats--is it related to advanced glycation end product formation?

Little is known about the mechanisms for the biomechanical remodeling in diabetes. The histomorphology, passive biomechanical properties and expression of advanced glycation end product (N epsilon-(carboxymethyl) lysine, AGE) and its receptor (RAGE) were studied in jejunal segments from 8 GK diabetic rats (GK group) and 10 age-matched normal rats (Normal group). The mechanical test was done by using a ramp distension of fluid into the jejunal segments in vitro. Circumferential stress and strain were computed from the length, diameter and pressure data and from the zero-stress state geometry. AGE and RAGE were detected by immunohistochemistry staining. Linear regression analysis was done to study association between the glucose level and AGE/RAGE expression with the histomorphometric and biomechanical parameters. The blood glucose level, the jejunal weight per length, wall thickness, wall area and layer thickness significantly increased in the GK group compared with the Normal group (P<0.05, P<0.01 and P<0.001). The opening angle and absolute values of residual strain decreased whereas the circumferential stiffness of the jejunal wall increased in the GK group (P<0.05 and P<0.01). Furthermore, stronger AGE expression in the villi and crypt and RAGE expression in the villi were found in the GK group (P<0.05 and P<0.01). Most histomorphometric and biomechanical changes were associated with blood glucose level and AGE/RAGE expression. In conclusion, histomorphometric and biomechanical remodeling occurred in type 2 diabetic GK rats. The increasing blood glucose level and the increased AGE/RAGE expression were associated with the remodeling, indicating a causal relationship.

Effect of Tangweian Jianji on upper gastrointestinal remodeling in streptozotocin-induced diabetic rats

AIM: To investigate the effect of Tangweian Jianji (TWAJJ) on the biomechanical and morphometrical remodeling of the upper gastrointestinal tract in diabetic rats.

METHODS: Diabetes was induced in 27 rats by injecting streptozotocin (40 mg/kg body weight), the animals were then divided into three groups (n = 9 in each group), i.e., diabetic control (DM); high dose (10 g/kg, T1) and low dose (5 g/kg, T2). Another 10 rats acted as normal controls (Control). TWAJJ was administered by gavage once daily. Blood glucose and serum insulin levels were measured. Circumferential length, wall thickness and opening angle were measured from esophageal, duodenal, jejunal and ileal ring segments. The residual strain was calculated from the morphometric data. Step-wise distension was carried out on esophageal and jejunal segments. The obtained data on the length, diameter and pressure changes were then used to calculate the circumferential and longitudinal stresses and strains. Real-time reverse transcription polymerase chain reaction was used to detect the receptor of advanced glycation end-products (RAGE) mRNA level in jejunal tissues.

RESULTS: At the end of the experiment, the blood glucose level was significantly higher and the serum insulin level was significantly lower in DM, T1 and T2 groups than in the control group (Glucose: 30.23 ± 0.41 mmol/L, 27.48 ± 0.27 mmol/L and 27.84 ± 0.29 mmol/L vs 5.05 ± 0.04 mmol/L, P = 1.65 × 10^-16, P = 5.89 × 10^-19 and P = 1.63 × 10^-18, respectively; Insulin: 1.47 ± 0.32 μg/L, 2.66 ± 0.44 μg/L, 2.03 ± 0.29 μg/L and 4.17 ± 0.54 μg/L, P = 0.0001, P = 0.029 and P = 0.025, respectively). However, these levels did not differ among the DM, T1 and T2 groups. The wet weight per unit length, wall thickness and opening angle of esophageal and intestinal segments in the DM group were significantly higher than those in the control group (from P = 0.009 to P = 0.004). These parameters in the T1 group were significantly lower than those in the DM group (wet weight, duodenum: 0.147 ± 0.003 g/cm vs 0.158 ± 0.001 g/cm, P = 0.047; jejunum, 0.127 ± 0.003 g/cm vs 0.151 ± 0.002 g/cm, P = 0.017; ileum, 0.127 ± 0.004 g/cm vs 0.139 ± 0.003 g/cm, P = 0.046; wall thickness, esophagus: 0.84 ± 0.03 mm vs 0.94 ± 0.02 mm, P = 0.014; duodenum: 1.27 ± 0.06 mm vs 1.39 ± 0.05 mm, P = 0.031; jejunum: 1.19 ± 0.07 mm vs 1.34 ± 0.04 mm, P = 0.047; ileum: 1.09 ± 0.04 mm vs 1.15 ± 0.03 mm, P = 0.049; opening angle, esophagus: 112.2 ± 13.2˚ vs 134.7 ± 14.7˚, P = 0.027; duodenum: 105.9 ± 12.3˚ vs 123.1 ± 13.1˚, P = 0.046; jejunum: 90.1 ± 15.4˚ vs 115.5 ± 13.3˚, P = 0.044; ileum: 112.9 ± 13.4˚ vs 136.1 ± 17.1˚, P = 0.035). In the esophageal and jejunal segments, the inner residual stain was significantly smaller and the outer residual strain was larger in the DM group than in the control group (P = 0.022 and P = 0.035). T1 treatment significantly restored this biomechanical alteration (P = 0.011 and P = 0.019), but T2 treatment did not. Furthermore, the circumferential and longitudinal stiffness of the esophageal and jejunal wall increased in the DM group compared with those in the control group. T1, but not T2 treatment, significantly decreased the circumferential wall stiffness in the jejunal segment (P = 0.012) and longitudinal wall stiffness in the esophageal segment (P = 0.023). The mRNA level of RAGE was significantly decreased in the T1 group compared to that in the DM group (P = 0.0069).

CONCLUSION: TWAJJ (high dose) treatment partly restored the morphometric and biomechanical remodeling of the upper gastrointestinal tract in diabetic rats.

A novel 3D shape context method based strain analysis on a rat stomach model

The stomach has the ability to change its geometry and volume during digestion. Thus, the stomach shape changes dynamically due to changes in contents and due to pressure from adjacent organs. Full-field strain analysis is therefore important for accurate estimation of the true deformation in this highly non-homogeneous, anisotropic organ. The aim of this study is to introduce a modified non-rigid image registration based 3D shape context method combined with a full-field strain analysis method to describe a distension-induced 3D gastric deformation. The geometry of a normal rat stomach at distension pressures from 0.05 kPa to 0.8 kPa were obtained by ultrasonic scanning. The full-field strain distribution of the 3D gastric model between the reference state and the distended state were computed on the basis of the improved 3D shape context method and full-field strain analysis method. The registered surface showed a good agreement with the real deformed surface for all distension states. However, the errors increased with the distension pressure due to increasing dissimilarity between the deformed and the reference surface. The strain distributions on the stomach surface were non-uniform with the largest deformation in the non-glandular part and the greater and lesser curvature when the pressure was higher than 0.2 kPa. The wall stiffness of the non-glandular part was softer than that of the glandular part. The modelling analysis method which is closely allied with the non-rigid image registration and strain analysis provides a kinematically possible deformation mode of the gastric wall. This method can be potentially used for clinical data estimating the kinematical properties of the human visceral organs in health and disease.

Biomechanical and histomorphometric colon remodelling in STZ-induced diabetic rats

The histomorphologic and passive biomechanical properties were studied in the mid-colon of 16 non-diabetic and 20 streptozotocin (STZ)-induced diabetic rats (50 mg/kg STZ, ip). The diabetic rats were divided into groups living 4 and 8 weeks after the induction of diabetes (n = 10 for each group). The mechanical test was a ramp distension of fluid into the colon in vitro. The colon diameter and length were obtained from digitized images of the segments at pre-selected pressures and at the no-load and zero-stress states. Circumferential and longitudinal stresses and strains were computed from the length, diameter, and pressure data and from the zero-stress state geometry. The blood glucose level increased 3-4-fold in the diabetic rats compared with the controls (P < 0.001). Diabetes generated pronounced increases in the colon weight per length, wall thickness, and wall cross-sectional area (P < 0.001). Histologically, the thickness of all layers was increased during diabetes (P < 0.05), especially the mucosa layer. The opening angle, and absolute values of residual strain increased in the diabetic group (P < 0.05 and P < 0.01, respectively). Furthermore, diabetes increased the circumferential and longitudinal stiffness of the colon wall (P < 0.001). The observed changes in residual strain, opening angle, and stress-strain relation may be contributing factors to colonic dysfunction and abdominal pain in diabetic patients.

Characterization of upper thoracic spinal neurons responding to esophageal distension in diabetic rats

The aim of this study was to examine spinal neuronal processing of innocuous and noxious mechanical inputs from the esophagus in diabetic rats. Streptozotocin (50 mg/kg, ip) was used to induce diabetes in 15 male Sprague-Dawley rats, and vehicle (10 mM citrate buffer) was injected into 15 rats as control. Four to eleven weeks after injections, extracellular potentials of single thoracic (T3) spinal neurons were recorded in pentobarbital anesthetized, paralyzed, and ventilated rats. Esophageal distensions (ED, 0.2, 0.4 ml, 20 s) were produced by water inflation of a latex balloon in the thoracic esophagus. Noxious ED (0.4 ml, 20 s) altered activity of 44% (55/126) and 38% (50/132) of spinal neurons in diabetic and control rats, respectively. The short-lasting excitatory responses to ED were encountered more frequently in diabetic rats (27/42 vs 15/41, P<0.05). Spinal neurons with low threshold for excitatory responses to ED were more frequently encountered in diabetic rats (33/42 vs 23/41, P<0.05). However, mean excitatory responses and duration of responses to noxious ED were significantly reduced for high-threshold neurons in diabetic rats (7.4+/-1.1 vs 13.9+/-3.3 imp/s; 19.0+/-2.3 vs 31.2+/-5.5 s; P<0.05). In addition, more large size somatic receptive fields were found for spinal neurons with esophageal input in diabetic rats than in control rats (28/42 vs 19/45, P<0.05). These results suggested that diabetes influenced response characteristics of thoracic spinal neurons receiving mechanical esophageal input, which might indicate an altered spinal visceroceptive processing underlying diabetic esophageal neuropathy.

Gastrointestinal tract modelling in health and disease

The gastrointestinal (GI) tract is the system of organs within multi-cellular animals that takes in food, digests it to extract energy and nutrients, and expels the remaining waste. The various patterns of GI tract function are generated by the integrated behaviour of multiple tissues and cell types. A thorough study of the GI tract requires understanding of the interactions between cells, tissues and gastrointestinal organs in health and disease. This depends on knowledge, not only of numerous cellular ionic current mechanisms and signal transduction pathways, but also of large scale GI tissue structures and the special distribution of the nervous network. A unique way of coping with this explosion in complexity is mathematical and computational modelling; providing a computational framework for the multilevel modelling and simulation of the human gastrointestinal anatomy and physiology. The aim of this review is to describe the current status of biomechanical modelling work of the GI tract in humans and animals, which can be further used to integrate the physiological, anatomical and medical knowledge of the GI system. Such modelling will aid research and ensure that medical professionals benefit, through the provision of relevant and precise information about the patient’s condition and GI remodelling in animal disease models. It will also improve the accuracy and efficiency of medical procedures, which could result in reduced cost for diagnosis and treatment.

Biomechanical functional and sensory modelling of the gastrointestinal tract

The aim of this review is to describe the biomechanical, functional and sensory modelling work that can be used to integrate the physiological, anatomical and medical knowledge of the gastrointestinal (GI) system. The computational modelling in the GI tract was designed, implemented and evaluated using a series of information and communication technologies-based tools. These tools modelled the morphometry, biomechanics, functions and sensory aspects of the human GI tract. The research presented in this review is based on the virtual physiological human concept that pursues a holistic approach to representation of the human body. Such computational modelling combines imaging data, GI physiology, the gut-brain axis, geometrical and biomechanical reconstruction, and computer graphics for mechanical, electronic and pain analysis. The developed modelling will aid research and ensure that medical professionals benefit through the provision of relevant and precise information about a patient's condition. It will also improve the accuracy and efficiency of the medical procedures that could result in reduced cost for diagnosis and treatment.

Effect of Kaiyu Qingwei Jianji on the morphometry and residual strain distribution of small intestine in experimental diabetic rats

AIM: To investigate the effect of a Chinese medicine, Kaiyu Qingwei Jianji (KYQWJJ) used for diabetic treatment, on the morphometry and residual strain distribution of the small intestine in streptozotocin (STZ) -induced diabetic rats. Correlation analysis was also performed between the opening angle and residual strain with the blood glucose level.

METHODS: Forty-two male Wistar rats weighing 220-240 g were included in this study. Thirty-two STZ-induced diabetic rats were subdivided into four groups (n = 8 in each group), i.e. diabetic control group (DM); high dose of KYQWJJ (T1, 36g/kg per day); low dose of KYQWJJ (T2, 17 g/kg per day) and Gliclazide (T3, 50 mg/kg per day). Another ten rats were used as non-diabetic control (CON). The medicines were poured directly into stomach lumen by gastric lavage twice daily. The rats of CON and DM groups were only poured the physiological saline. Blood glucose and plasma insulin levels were measured. Experimental period was 35 d. At the end of experiment, three 5-cm long segments were harvested from the duodenum, jejunum and ileum. Three rings of 1-2 mm in length for no-load and zero-stress state tests were cut from the middle of different segments. The morphometric data, such as the circumferential length, the wall thickness and the opening angle were measured from the digitized images of intestinal segments in the no-load state and zero-stress state. The residual strain was computed from the morphometry data. Furthermore, the linear regression analysis was performed between blood glucose level with morphometric and biomechanical data in the different intestinal segments.

RESULTS: The blood glucose level of DM group was consistent 4-fold to 5-fold higher than those in CON group during the experiment (16.89 ± 1.11 vs 3.44 ± 0.15 mmol/L, P < 0.001). The blood glucose level in the T1 (16.89 ± 1.11 vs 11.08 ± 2.67 mmol/L, P < 0.01) and T3 groups (16.89 ± 1.11 vs 13.54 ± 1.73 mmol/L, P < 0.05), but not in T2 group (P > 0.05) was significantly lower than those in DM group. The plasma insulin levels of DM, T1, T2 and T3 groups were significantly lower than those in CON group (10.98 ± 1.02, 12.52 ± 1.42,13.54 ± 1.56,10.96 ± 0.96 vs 17.84 ± 2.34 pmol/L respectively, P < 0.05), but no significantly difference among the groups with exception of CON group. The wet weight/cm and total wall thickness of duodenum, jejunum and ileum in DM group were significantly higher than those in CON group (wet weight (g/cm): duodenum 0.209 ± 0.012 vs 0.166 ± 0.010, jejunum 0.149 ± 0.008 vs 0.121 ± 0.004, ileum 0.134 ± 0.013 vs 0.112 ± 0.007; Wall thickness (mm): duodenum 0.849 ± 0.027 vs 0.710 ± 0.026, jejunum 0.7259 ± 0.034 vs 0.627 ± 0.025, ileum 0.532 ± 0.023 vs 0.470 ± 0.010, all P < 0.05), T1 and T3 treatment could partly restore change of wall thickness, but T2 could not. The opening angle and absolute value of inner and outer residual stain were significantly smaller in duodenal segment (188 ± 11 degrees, -0.31 ± 0.02 and 0.35 ± 0.03 vs 259 ± 15 degrees, -0.40 ± 0.02 and 0.43 ± 0.05) and larger in jejunal (215 ± 20 degrees, -0.30 ± 0.03 and 0.36 ± 0.06 vs 172 ± 19 degrees, -0.25 ± 0.02 and 0.27 ± 0.02) and ileal segments (183 ± 20 degrees, -0.28 ± 0.01 and 0.34 ± 0.05 vs 153 ± 14 degrees, -0.23 ± 0.03 and 0.29 ± 0.04) in DM group than in CON group (P < 0.01). T1 and T3 treatment could partly restore this biomechanical alteration, but strong effect was found in T1 treatment (duodenum 243 ± 14 degrees, -0.36 ± 0.02 and 0.42 ± 0.06, jejunum 180 ± 15 degrees, -0.26 ± 0.03 and 0.30 ± 0.06 and ileum 163 ± 17 degrees, -0.23 ± 0.03 and 0.30 ± 0.05, compared with DM, P < 0.05). The linear association was found between the glucose level with most morphometric and biomechanical data.

CONCLUSION: KYQWJJ (high dose) treatment could partly restore the changes of blood glucose level and the remodeling of morphometry and residual strain of small intestine in diabetic rats. The linear regression analysis demonstrated that the effect of KYQWJJ on intestinal opening angle and residual strain is partially through its effect on the blood glucose level.

Upper gastrointestinal sensory-motor dysfunction in diabetes mellitus

Gastrointestinal (GI) sensory-motor abnormalities are common in patients with diabetes mellitus and may involve any part of the GI tract. Abnormalities are frequently sub-clinical, and fortunately only rarely do severe and life-threatening problems occur. The pathogenesis of abnormal upper GI sensory-motor function in diabetes is incompletely understood and is most likely multi-factorial of origin. Diabetic autonomic neuropathy as well as acute suboptimal control of diabetes has been shown to impair GI motor and sensory function. Morphological and biomechanical remodeling of the GI wall develops during the duration of diabetes, and may contribute to motor and sensory dysfunction. In this review sensory and motility disorders of the upper GI tract in diabetes is discussed; and the morphological changes and biomechanical remodeling related to the sensory-motor dysfunction is also addressed.